What is the function of "yang" in this sentence? Wouldn't the sentence mean the same without it?
I believe yang can be used for emphasis. If they are choosing between a red dress and a blue dress you would use 'yang'. If no emphasis on the color is needed yang can be omitted.
'Yang' is usually used to translate relative pronouns. I think it's unnecessary to use 'yang' in this sentence.
They take the dress that is red?
I had the same translation. Isn't "yang" to emphasize the dress's redness?
Why not: they get that red dress?
Yes, why is this marked wrong?